The present invention relates generally to thermostatic valves, and more particularly to thermostatic valves that are electronically controlled.
Currently used thermostatic valves control inlet temperatures of streams that are eventually output through a faucet, showerhead, or other outlet device. The thermostatic valve may, for example, adjust the amount of hot and cold water flowing to an outlet stream to compensate for changes in the inlet stream pressure and/or temperature, ensuring that the outlet stream temperature remains steady. Known high flow capacity valves can maintain an equilibrium temperature if pressure and/or temperature changes (e.g., those caused by a toilet flushing) occur at the inlet when carrying flow amounts near the upper capacity of the valve. However, the same high flow capacity valves have trouble maintaining an equilibrium outlet temperature when carrying flow amounts below the valve""s capacity, such as in applications using only one showerhead, when pressure and/or temperature changes occur at the inlet.
Further, some thermostatic valves designed for high flow (e.g., more than 10 gallons per minute) applications tend to be unstable if used in low flow applications (e.g., less than 2.5 gallons per minute), causing the output temperature to oscillate by as much as 10-15xc2x0 F. if sudden pressure reductions occur. Currently available thermostatic valves are designed to operate either in high outlet flow or low outlet flow environments, but there are no known thermostatic valves that can operate in different flow environments without a decrease in performance.
There is a desire for a thermostatic valve system that can maintain an equilibrium temperature during sudden pressure changes and that can perform acceptably in both low flow and high flow applications.
The present invention is directed to a system having an electronically-controlled thermostatic valve. An electronic control module (ECM) is connected to a motor that controls a thermostatic valve. The ECM sends an electric signal corresponding to a desired outlet stream temperature to the motor, which turns the thermostatic valve to a location approximately corresponding to the desired temperature. A temperature sensor disposed in the outlet stream may send a feedback signal to the ECM so that the ECM can adjust the motor, and therefore the thermostatic valves, to reach the desired temperature exactly.
In one embodiment, the system also includes inlet motors that control valves on the inlet supplies. If the ECM detects that the outlet flow demands of the system are lower than the thermostatic valve""s capacity, the ECM can lower the valve capacity by restricting the valves on the inlet supplies via the inlet motors. By controlling the inlet flow, the system can vary the thermostatic valve capacity according to outlet flow demands to ensure that the valve can maintain an equilibrium temperature in the outlet stream even if there are sudden pressure changes within the system.
Electronically controlling a mechanically-operated thermostatic valve and incorporating inlet restrictions creates a variable-capacity thermostatic valve that operates acceptably in both low flow and high flow environments. Further, using an ECM-controlled thermostatic valve instead of more complicated electronic controllers keeps the system design simple and easy to service.